1. Field of the Invention
The present invention relates to a rear wheel suspension for a vehicle and, more particularly, to a suspension which can enhance riding comfort by absorbing vibration generated when a wheel moves upward and downward by means of a shock-absorbing member, and which can cope with shock and minute vibration by making a displacement of the shock-absorbing member larger than that of a wheel.
2. Description of Related Art
In general, a conventional vehicle suspension connects an axle shaft and a vehicle body to each other and absorbs an impact and vibration from a road surface to increase riding comfort and running safety. To absorb the impact from the road surface, a connection between upper and lower parts should be flexible, and to cope with driving and breaking forces applied to a wheel and a centrifugal force in a vehicle's turning, a connection in a horizontal direction of the suspension should be durable.
Suspension systems are structurally characterized as an integral shaft suspension and an independent suspension. The suspension of this invention concerns the independent suspension. These include the McPherson strut type suspension and Wishbone type suspensions.
The McPherson strut type suspension system comprises a strut arm 55, a shock-absorbing means, consisting of a shock absorber 51 and a spring 52 and having a lower part fixed to a wheel carrier 53 pivotally supporting a wheel 50 and an upper part supported by a vehicle body; and a lower control arm 56 connecting the lower part of the wheel carrier 53 to the lower part of the vehicle body, as shown in FIG. 4A.
The Wishbone type suspension system, as shown in FIG. 4B, includes the wheel carrier 53 supporting the wheel 50 and having the upper and lower parts connected to a sub-frame 54 of a car body by the upper and lower control arms 57 and 58, respectively, and a spring 59, as an absorbing means, disposed between the upper and lower control arms.
The above-mentioned two kinds of the conventional suspension systems include in common an absorbing member mounted vertically or inclined a little, such that the shock applied from the wheel is directly transmitted to the shock-absorber member, whereby the suspensions have problems that there is a limit to the release of the shock and the enhancement in the riding comfort which place restrictions on the layout of the suspension system.
In addition, the suspension system is designed to have a spring rate of the shock-absorbing member larger than a wheel rate or a suspension rate, and the controlling function against the minute displacement is not precise at an initial stage. Thus, the conventional suspension systems have a problem of not being able to cope with minute vibration.